1. Field of the Invention
The present invention generally relates to a self-routing switch device such as an ATM (Asynchronous Transfer Mode) device, and more particularly to an ATM device which can be connected to another ATM device through a plurality of transmission lines and can set a connection of an SVC (Switched Virtual Connection) call.
Recently, an ISDN (Integrated Services Digital Network) has been practically used as a network in which voice data and communication data can be transferred at a high speed. However, such an ISDN may be insufficient to transfer video data of a high quality.
Now, an ATM is used to realize a multimedia communication capable of transferring all kinds of data such as voice data, communication data and video data due to the recent development and advance of an optical fiber communication technique having a capability of realizing large-capacitance communication and a digital technique of digitizing all communication data.
2. Description of the Related Art
Referring to FIG. 1, the setting of an SVC call in an ATM device which is one of the self-routing switches will be described.
An ATM device la and an ATM device 1b are connected together by two transmission lines A and B, each of which lines has a band equal to 156 Mbps. FIG. 1 shows a state in which a connection of an SVC call between terminals A and O is set on the transmission line A, and a connection of an SVC call between terminals D and R is set on the line B.
Further, a connection of an SVC call between terminals D and R is released so that the line A has an idle band equal to 81 Mbps. Similarly, the line B has an idle band equal to 81 Mbps.
If a communication between the terminals C and Q takes place, the ATM device la receives, from the terminal C, a call setup request which requests a band equal to, for example, 50 Mbps. Then, the ATM device la recognizes a called ATM device and determines a route by referring to a called identification number provided in the call setup request. In this case, the called ATM device is the terminal Q. In FIG. 1, the terminal Q is connected to the ATM device 1b, and thus the ATM device 1a selects the lines A and B, which are routes connected to the ATM device 1b. The ATM device 1a selects a line which meets the requested band 50 Mbps from the selected routes, and sets the SVC call connection. Since each of the lines A and B respectively has an idle band of 81 Mbps, the ATM device 1a can set the SVC call connection to either the line A or B.
As shown in FIG. 1, if the terminals A and Q communicate with each other, the ATM device 1a receives, from the terminal C, a call setup request which requests 100 Mbps band. Then, the ATM device 1a recognizes a called ATM device and determines a route by referring to a called identification number provided in the call setup request. In FIG. 1, the terminal Q is connected to the ATM device 1b, and thus the ATM device 1a selects the lines A and B, which are routes connected to the ATM device 1b. The ATM device 1a selects a line which meets the requested band 100 Mbps from the selected routes, and sets the SVC call connection. However, each of the lines A and B has an idle band of 81 Mbps, and thus, the ATM device 1a cannot set the connection. That is, if the requested band is not available in any of the lines connected to the called ATM device, the ATM device 1a cannot set the connection.
The ATM device cannot set a connection of an SVC call if each of the lines does not meet the requested band although each of the lines has a respective idle band. Hence, even if the total of the idle bands meets the requested band, the ATM device cannot set a connection of an SVC call. Hence, the ATM device efficiently cannot utilize the line capacity.
It is an object of the present invention to provide an ATM device in which the above disadvantages are eliminated.
A more specific object of the present invention is to provide an ATM device capable of setting a connection even if each line connected to a called ATM device does not have an idle band as much as a requested band.
The above objects of the present invention are achieved by an ATM device which can be connected to an ATM network via lines, the ATM device comprising: a first part setting connections on the lines; and a second part moving a connection on a line to another line if a call setup requests a band greater than idle bands of the lines so that the band requested by the call setup can be set on the line from which the connection is moved.
The ATM device may further comprises a control information memory part which stores control information concerning states of the lines and states of connections set on the lines, the second part moves the connection by referring to the control information.
The ATM device may be configured so that the second part comprises: a connection search part which searches for a connection set on a line to be moved to another line by referring to control information concerning states of the lines and states of connections set on the lines; a line selecting part which selects a line to which the connection searched for should be moved by referring to the control information; and a rearrangement part which moves the connection searched for to the line selected by the line selecting part.
The ATM device may be configured so that the second part moves a connection on a line which has a minimum idle band after the connection is moved, as compared to the idle bands of the other lines.
The ATM device may be configured so that the connection search part searches for a connection on a line which has a minimum idle band after the connection is moved, as compared to the idle bands of the other lines.
The ATM device may be configured so that the second part moves a connection from a line which allows connections to be moved therefrom.
The ATM device may be configured so that: the control information memory part includes information indicating types of the connections; and the connection search part searches for a connection from a line which allows connections to be moved therefrom by referring to the types of the connections.
The ATM device may be configured so that the second part moves a connection from a line to another line which has a maximum idle band after receiving the connection moved, as compared to idle bands of the other lines by referring to the control information.
The ATM device may be configured so that the connection search part searches for a connection set on a line to be moved to another line which has a maximum idle band after receiving the connection moved, as compared to idle bands of the other lines by referring to the control information.
The ATM device may be configured so that the second part moves a connection from a line to another line in accordance with types of connections.
The ATM device may be configured so that:
the control information memory part includes information indicating types of the connections; and the line selecting part selects a line to which the connection should be moved by referring to the types of the connections.
The ATM device may be configured so that the second part moves a connection from a line to another line in accordance with priority assigned to the lines.
The ATM device may be configured so that:
the control information memory part includes information indicating priority assigned to the lines; and the line selecting part selects a line to which the connection should be moved by referring to the priority.
The ATM device may further comprise a periodic monitor part which periodically monitors states of the lines and states of connections set thereon and obtain information concerning the states thereof, the second part moving a connection set on a line to another line in accordance with the information obtained by the periodic monitor part.
The ATM device may be configured so that the second part periodically moves a connection on a line to another line in accordance with priority assigned to the lines.
The ATM device may be configured so that the second part periodically moves a connection on a line to another line so that idle bands of the lines are averaged.
The ATM device may be configured so that the second part moves a connection on a line from another line in accordance with information which is asked to be checked by a request of the call setup and prevents a connection which is not allowed to be moved to another line from being moved.
The ATM device may be configured so that the connection search part refers to information which is asked to be checked by a request of the call setup and prevents a connection which is not allowed to be moved to another line from being moved and searches for the line.